Inkjet printing is a non-impact method for producing printed images by the deposition of ink drops in a pixel-by-pixel manner onto a suitable substrate in response to digital signals. There are various printing methods and apparatus known in the art to control the deposition of ink drops including what are considered “drop-on-demand” (DOD) printing systems and “continuous ink jet” (CIJ) printing systems. For DOD printing systems, individual ink drops are projected as needed onto a substrate using various means for droplet deposition control. DOD printing systems are widely used in home or consumer inkjet printers that have been available for several decades.
Colored pigment-based inks have been proposed as a means for addressing limitations of dye-based inks. In pigment-based inks, the colorant exists as discrete particles, and such particles can be present as self-dispersed or encapsulated materials, or they can be dispersed and stabilized using polymers or various surfactants. A wide variety of pigments can be chosen for use in this manner depending upon the specific application and performance characteristics of the printing system and desired printing results.
More recently, there has been a greater need for aqueous inkjet ink compositions that can be used to print images onto textiles such as clothing, draperies, carpeting, household linens, leather, and any porous or non-porous material made from natural or synthetic fibers. However, such applications of inkjet printing technology require additional features than may be necessary for other substrates, including for example improved color fastness and wash (laundry) fastness. Inkjet printed fabrics are particularly susceptible to color image removal by repeated laundering and other abrasion actions including the usual wearing (for clothing and bed linens) or foot traffic (for carpeting) and have limited durability. For example, printed colors may fade upon repeated washing and pigmented colorants may transfer to washing machine parts or be washed into the environment or sewage treatment facilities.
Polyurethanes have been known for several years as useful additives to particle-based inkjet ink compositions. For example, polyurethanes are described for use in green colored particle-based inkjet ink compositions for use in both DOD and CIJ printing operations in U.S. Pat. No. 9,605,169 (Lussier et al.), and as part of core-shell particles dispersed within inkjet ink compositions described in U.S. Pat. No. 9,145,502 (Brust et al.).
U.S. Pat. No. 7,074,850 (Hees et al.) describes crosslinkable polyurethane block copolymers for colorant preparations for use in inkjet printing.
U.S. Pat. No. 8,186,822 (Li et al.) describes the use of crosslinked polyurethane dispersoid binder additives in inkjet inks for printing textiles. Such materials are prepared from a unique set of diols to allegedly provide improved durability and color fastness of inkjet printed color images on textiles.
While there have been advances in the field of inkjet printing of particle-based (pigment-based) inkjet ink compositions, including their use to provide color images on textile, there is a continuing need to improve the light fastness and color fastness of such color images especially after multiple laundering and continual abrasive uses. The present invention is directed to providing such an improvement.